There is a case that ink-jet recording is performed using a treatment liquid that contains a polyvalent metal ion such as a calcium ion (Ca2+) in order to increase an optical density (an OD value) of a recorded object. The polyvalent metal ion contained in the treatment liquid can cause a self-dispersing pigment in a water-based ink to aggregate, resulting in increasing an optical density (an OD value) of the recorded object.
However, in an ink-jet recording method using a conventional treatment liquid, a polyvalent metal ion in the treatment liquid causes generation of insoluble salt, resulting in nozzle clogging in an ink-jet head or a blockage of a flow path of the treatment liquid in an ink-jet recording apparatus.